Many types of devices that project stereoscopically viewable images have conventionally been proposed, for example in Patent Documents 1 and 2. The devices according Patent Documents 1 and 2 each incorporate two display elements, such as liquid crystal display elements, which display right-eye and left-eye images respectively, which are then projected via respective projection lenses onto a screen. Here, putting the right-eye and left-eye images in different polarization states and requiring the viewer to wear polarizing glasses permits him to view a stereoscopic image. Employing a lenticular plate to split the right-eye and left-eye images to the viewer's right and left eyes, respectively, permits him to view a stereoscopic image even without wearing polarizing glasses.
On the other hand, Patent Document 3 discloses (1) a device that projects, through two projection lenses, two intermediary images obtained by polarization splitting and polarization conversion within a relay optical system; (2) a device that projects, through a single projection lens, one double-size intermediary image obtained by polarization splitting and polarization conversion at the pupil position of a relay optical system; and (3) a device that projects an image by polarization splitting and polarization conversion within a projection lens without the use of a relay optical system. In all these projection methods, one of the polarization-split lights is polarization-converted and, with polarization aligned, the polarization direction is switched at high speed; this permits a viewer wearing polarizing glasses to view a stereoscopic image.